The goal of the proposed research is to systematically explore areas of overlap and divergence in cognitive-linguistic processing between typically developing school-age children who speak English as a first language, Spanish-speakers who have learned English as their second (L2) language, and monolingual English-speaking children with a primary language impairment (LI). Two studies are proposed to test the predictions of a general interactive information processing theory as applied to the joint study of LI and L2 acquisition by children. Study 1 (Language-Dependent Measures) tests processing skills in English on non-word repetition and lexical retrieval tasks. The prediction here is that L2 learners and children with LI will perform similarly, and that this performance will be significantly below (slower and/or less accurate) than that of their intact monolingual English-speaking peers. Study 2 (Nonlinguistic Cognitive Measures) tests basic-level cognitive processing on nonlinguistic auditory perception and visual working memory tasks. Previous research has shown that children with LI perform more poorly than their language-intact (monolingual) peers on these tasks. Contrary to the results of Study 1, we hypothesize that there will be no difference between typical monolingual and L2 children in Study 2, with both groups having greater task speed/accuracy than children with LI. The long-term goal of the research is to identify common non-linguistic processing ground which separates intact from impaired language learners (regardless of diverse language experience) within an interactive information-processing framework of language learning and breakdown. Pending empirical support for the current hypotheses, future research will be expanded to more precisely define the nature of errors in cognitive-linguistic processing in L2 learners with and without LI. A major aim of this innovative line of research is to develop a specific model of L2 acquisition as it interacts with LI. This explicit theoretical processing model of language learning by L2 learners with and without LI is needed in order to develop clinical measures which can be used to identify LI in the highly variable population of L2 learners.